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Section 26 USB 2.0 Host/Function Module
R01UH0134EJ0400 Rev. 4.00 Page 1519 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
(b) REW Bit
It is possible to temporarily stop access to the pipe currently being accessed, access a different
pipe, and then continue processing using the current pipe once again. The REW bit in
C/DnFIFOSEL is used for this.
If a pipe is selected when the REW bit is set to 1 and at the same time the CURPIPE bit in
C/DnFIFOSEL is set, the pointer used for reading from and writing to the buffer memory is reset,
and reading or writing can be carried out from the first byte. Also, if a pipe is selected with 0 set
for the REW bit, data can be read and written in continuation of the previous selection, without the
pointer used for reading from and writing to the buffer memory being reset.
To access the FIFO port, FRDY = 1 must be ensured after selecting a pipe.
(c) Accessing FIFO Port for Odd Data
For reading data from the FIFO port, when the number of data bits to be read is smaller than the
access width specified by the MBW bits in the FIFO port select registers, read the data with the
specified width and discard the unnecessary bits through software.
For writing data to the FIFO port, when the number of data bits to be written is smaller than the
access width specified by the MBW bits in the FIFO port select registers, access the registers as
shown in the following examples. In the examples, the FIFO port access width is 32 bits (MBW =
10) and 24-bit data is written to the FIFO port.